Some scientific data support the use of medical marijuana in MS, but only for certain symptoms and only in certain forms—which do not include smoked marijuana.
While the marijuana plant contains more than 400 chemicals, fewer than 100 have any physiologic effect. Two of the most-studied marijuana chemicals belong to a group called cannabinoids. These are:
- THC (delta-9-tetrahydrocannabinol), the chemical that is most responsible for marijuana’s psychoactive effects. If a person is using a medical marijuana product and “gets high,” this effect is mostly due to THC. However, THC may have additional medically important effects.
- CBD (cannabidiol), chemically related to THC, but without the psychoactive effects. CBD seems to have important pharmacologic effects, however. So a person using a product that is mostly CBD with much less THC—such as the one Williamson uses—is much less likely to feel any “high,” but may still get medical benefit.
A panel was selected by the American Academy of Neurology (AAN) to carefully study all of the reports about CAM and MS published since 1970, and provide recommendations. The panel published a report in late March with its findings, including a section on medical marijuana.
The AAN report looked at studies that used natural marijuana, as well as three pharmaceutical preparations: Marinol, Sativex and and an “oral cannabis extract.” AAN experts found mixed evidence for all three products: They found strong evidence that OCE reduced study participants’ reports of spasticity and the pain caused by spasticity, and moderate evidence that Marinol does the same. Neither OCE nor Marinol reduced tremor symptoms, and there was not enough evidence to decide whether either of these help with bladder control.
With Sativex, the reviewers found moderate evidence that it reduced study subjects’ self-reported symptoms of spasticity, pain caused by spasticity, and frequent urination. (Despite this, the AAN panel found that the published research does not show a change in spasticity when assessed with objective or standardized measures by clinicians.) They also found that Sativex does not help treat loss of bladder control.
The reviewers did not find enough evidence to determine whether smoked marijuana or newer forms, such as marijuana vapors or infused foods, are safe or effective for treating any MS symptoms.
The AAN panel of experts recommends that a person with MS who is interested in medical marijuana should discuss its potential benefits and side effects with his or her doctor and weigh them carefully, in light of his or her particular medical profile.
The AAN panel pointed out that most of the studies conducted to date have been short-term. Much more research is needed to know whether marijuana or its components are safe for long-term use. Some of marijuana’s known side effects include:
- Difficulty with attention and concentration
- Dry mouth
- Increased spasticity (despite some users’ self-reported symptoms of reduced spasticity)
- Falling and loss of balance
- Nausea, vomiting and constipation
- Psychosis, depression and other psychological problems
- Memory problems
The potential for psychological problems is a particular worry, because people with MS are already at higher than average risk for cognitive changes related to information processing speed, memory and attention, among other functions, as well as for depression or suicide. (Because of this, if someone is taking medical marijuana and experiencing symptoms of cognitive changes or depression, he or she should contact his or her healthcare provider immediately.)
Another concern is the considerable variation that exists in today’s medical marijuana marketplace. The doses and ratios of THC and CBD in the pharmaceutical forms of medical marijuana (Marinol and Sativex) are fixed, as with any FDA-approved medication. But in tests by independent laboratories of other forms of marijuana, the amounts of THC, CBD and other active ingredients vary from sample to sample. This is why Williamson relies on a medical marijuana dispensary that voluntarily sends its products out for independent testing and shares the results with its patients.
Contaminants such as bacteria and fungi may also be present in smoked marijuana, Dr. Voth says. Williamson points out, too, that some growers of marijuana, like other farmers, may use pesticides as well as plant growth regulators or other agents that increase yield. The dispensary he uses has its products tested for purity as well as potency.